next gen... 4 cyl deactivation?

Jgstewart8 · December 24, 2005

Why are they not making the next generations EVERYTHING v8 at GM available with the new optional 4 cylinder deactivation thing they are doing on the new impala... that dodge is doing on the hemi... it helps on gas milage like 30% or something pretty good.

DMAX Daddy · December 24, 2005

If they could do that in the Duramax they would sell "butt tons" of them (official form of measurement for my neighbor).

65 mph on the freeway you might get 30 mpg!

Jgstewart8 · December 24, 2005

Does anyone know why they are not doing it? It would be the best of both worlds! You would have power when you need it... and milage when you need it!

Only downside is if you have pipes.. they would sound pretty bad sometimes I assume.

DMAX Daddy · December 25, 2005

I havent read where they are NOT doing it. Noone know, I just hope information starts "Leaking" soon cause I want a new truck and Im holding off to see what these look like.

ZZebes · January 2, 2006

Well guys although it sounds like a good idea i am really apprehensive about it only because of the way the lifters work on DOD(Displacement on Demand) scares me. The ones that deactivate are an electronically controlled lifter.

The consist of an electromagnet that holds them solid when they are in use but lets them collapse when deactivated. the reason this scares me is that the sleeve that contains the lifter in the block has copper contacts on it that deliver the power to the electromagnet.

The fuel delivery is sound because it is still controlled by the PCM but anyone who has had to limp home on a dead plug knows that a motor with a dead cylinder is a dog.

But my main concern is engine longevity and wear. Because the motor has to drag along the extra 4 pistons while propelling the truck. Also when the cylinders start back up if it is not completely in unison than it will be a rough start that could cause detonation if the spark kicks in at the wrong time.

Now i have driven my friends HEMI with DOD and it was pretty seamless... to begin with. but after 5000 miles the engine wouldn't start and the dealership ended up replacing the DOD damper, the lifters, and the PCM. and it still is really sluggish to respond.

So sorry for the long response.

Just my $0.02

duramaxHD · January 6, 2006

I dont think you'll ever see DOD on a Duramax...it just wouldnt work well with the already "rough" high compression nature of a diesel. I cant imagine how it would run on 4 cylinders...I know it runs really rough and badly when I only shut down ONE cylinder with a Tech 2...I dont want to see 4 cylinders shut down!! JMO....

--Ben

DMAX Daddy · January 6, 2006

I dont think you'll ever see DOD on a Duramax...it just wouldnt work well with the already "rough" high compression nature of a diesel. I cant imagine how it would run on 4 cylinders...I know it runs really rough and badly when I only shut down ONE cylinder with a Tech 2...I dont want to see 4 cylinders shut down!! JMO....

--Ben

<{POST_SNAPBACK}>

True Ben, wishful thinking....

Zane · January 14, 2006

I dont think you'll ever see DOD on a Duramax...it just wouldnt work well with the already "rough" high compression nature of a diesel. I cant imagine how it would run on 4 cylinders...I know it runs really rough and badly when I only shut down ONE cylinder with a Tech 2...I dont want to see 4 cylinders shut down!! JMO....

--Ben

True, but with 4 down, at least things would be balanaced again. Think how off the forces are with only one turned off. I bet it would run pretty smooth with only 4, however who knows what it would sound like.

mmmikkke · January 14, 2006

A few years back we rented a trailer-type air compressor for some serious sandblasting of some old farm implements. The air compressor consisted of a Ford 302 V8, with 4 cylinders providing the power, and the other 4 cylinders compressing the air.

That thing was as smooth as a baby's butt.

So it's possible that a V8 with 4 cylinders shut down can run smooth, and that part is interesting to me.

But the longevity question is still unanswered, especially remembering the mess that GM created the last time they tried this...was around 1980 and they had the Cadillac V-eight-six-four. Depending on power needs, either all 8, or 6, or 4 cylinders would be used, with the remaining cylinders shut down. Word was that once these cars got a few miles on them, the cylinder shutdowns were mostly all disabled by mechanics trying to restore drivability and smoothness, and after that point they just ran as V8's.

DMAX Daddy · January 14, 2006

Supposedly Didge Magnums are smooth as silk when switching back and forth. This isnt rocket science, is it?

Or is it a case of over-engineering ;)

67ChevyRedneck · January 16, 2006

I think I read an article where GM has already created a DOD diesel engine and it is being tested on city buses in California? I believe the trailblazers have had DOD for over a year now and the tahoes and impala have it. I believe the trucks are to have it for '07. I'm skeptical too. I like how they put the HD style front end on the '06 trucks, makes the front end look a lot better. I think I'm gonna pick up a "new" '06 in early '07 when GM tries to unload them to push the new body style. I also read a testing article on the new tahoes, and hwy mileage improved from about 19 hwy to 22 hwy. I think city improved from 16 to 17. To me that's not a significant enough improvement to justify getting new unproven technology, but it is a step in the right direction. My two cents.

ChasSidwa · January 18, 2006

For a DOD diesel, why can't it be done thru the injectors only. My powerstroke would shut off the injectors any time you took your foot off the throttle and were coasting. I think its less complicated then a gasser.

pknowles · January 18, 2006

For a DOD diesel, why can't it be done thru the injectors only. My powerstroke would shut off the injectors any time you took your foot off the throttle and were coasting. I think its less complicated then a gasser.

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They could do that and maybe help a little, but it may use more fuel. The whole point of DOD was to reduce the power used to pump air through the engine. If they just turned off the fuel to 4 cyl without effecting the valves then you are still using energy to pump air on those 4 dead cylinders, just like an air compressor. With DOD you are not openning the valves and the 4 dead cylinders act like a spring, returning most of the energy put into compessing the air.